This application is based on Japanese Patent Application No. 2000-164650 filed in Japan, the contents of which are incorporated hereinto by reference.
1. Field of the Invention
This invention relates to a polishing slurry suited for the polishing of electronic materials, magnetic materials and optical materials, a polishing method using the polishing slurry, and a process for fabricating semiconductor devices.
2. Description of the Related Art
In recent years, in order to achieve higher integration of semiconductor integrated circuits, wiring techniques more and more trend toward finer and more multilayered wiring. This has brought about a tendency toward a larger difference in height of interlayer insulating films. Because of this difference in height of interlayer insulating films, any wiring formed thereon may have a low processing precision and a low reliability. Hence, polishing techniques for improving smoothness of interlayer insulating films have become very important For example, Japanese Patent Application Laid-open No.9-22885 discloses chemical mechanical polishing of interlayer insulating films formed on semiconductor wafers.
Polishing slurries conventionally used for semiconductor substrate may include, e.g., as disclosed in Japanese Patent Application Laid-open No. 11-111657, an acidic (about pH 3) alumina slurry, a neutral silica slurry having silica particles dispersed therein as abrasive grains, and an alkaline silica slurry prepared by adding sodium hydroxide or the like to this neutral slurry. Besides these, as abrasive grains, this publication further discloses oxide particles such as alumina particles, titanium oxide particles and zirconium oxide particles obtained by hydrolyzing metal alkoxides.
Abrasive grains comprised of metals (inclusive of semi-metals) or metal oxides, used in these conventional polishing slurries, adhere to the surfaces of objects to be polished and to the interiors of polishing apparatus, e.g., to pads, dressers and so forth, and remain thereon after polishing to damage smoothness and film properties unless no measure is taken therefor. Accordingly, as a post treatment of polishing, as disclosed in, e.g., Japanese Patent Application Laid-open No. 9-22885, washing with an alkaline solution or scrubbing washing has been carried out. However, for the abrasive grains comprised of metals (inclusive of semi-metals) or metal oxides, used in these conventional polishing slurries, it has been difficult to be completely removed by washing, and has been very difficult to be removed by washing especially when the abrasive grains stand stuck in the semiconductor substrate.
Accordingly, an object of the present invention is to provide a polishing slurry whose abrasive grains having remained after polishing are removable with ease, a polishing method and a semiconductor device fabrication process which make use of this polishing slurry.
To achieve the above object, the present invention provides a polishing slurry comprising a dispersion medium and abrasive grains dispersed in the dispersion medium; the abrasive grains comprising a material having a solubility in the dispersion medium at normal temperature (25xc2x0 C.), of 0.001 g/100 g or higher. The present invention also provides a polishing slurry comprising a dispersion medium and abrasive grains dispersed in the dispersion medium; the abrasive grains comprising organic matter. In either of inorganic matter and organic matter, the abrasive grains may preferably have a solubility in the dispersion medium, of 0.001 g/100 g or higher, and more preferably 0.1 g/100 g or higher. In the case when the abrasive grains are comprised of organic matter, it may preferably have a melting point of 30xc2x0 C. or above so that it can be present in the state of a solid in usual polishing steps.
The present invention still also provides a polishing method of polishing an object to be polished by using any of these polishing slurries of the present invention, and a process for fabricating a semiconductor device by using such a method.